Abstract
Abstract Background Soil fertility is substantially influenced by soil organic matter quality and quantity. Much attention has also been given to glomalin content as one of the qualitative parameters of soil fertility. Glomalin content is considered an indicator of soil fertility due to its positive correlation with soil organic carbon. Aim This study aim to (i) determine the influence of different fertilization systems on maize yield and soil organic matter quality parameters, (ii) ensure that changes in total glomalin content (TG) and easily extractable glomalin (EEG) content are sensitive enough to reflect changes in the SOM quality resulting from long-term fertilization, and (iii) determine whether both forms of glomalin must be determined or if the easily extractable glomalin (EEG) content is sufficient, even for a fertile chernozem. Materials and methods Long-term field experiments with silage maize monocultures were used to study relationships under different rates of mineral nitrogen and sewage sludge fertilization. The trials comprised 5 treatments: (i) no fertilization control (Con), (ii) and (iii) two different calcium ammonium nitrate rates (N120 and N240 at doses of 120 and 240 kg N ha −1 year −1 , respectively), and iv) and v) two different sewage sludge rates (S120 and S240 corresponding to mineral N doses). Topsoil (0–30 cm) analysis was performed 28 years after the onset of the experiment to determine soil organic carbon, the fractions of humic substances, potentially mineralizable carbon and dissolved organic carbon, the potential wettability index, soil aggregate stability, EEG, and total glomalin (TG). Results The control treatment, which did not include fertilization, showed significantly lower average yields (9.76 t DM ha −1 year −1 ) than the fertilization treatments (on average 12.3 DM ha −1 year −1 ). Significant differences in yields were not found between the fertilization treatments. A positive correlation between glomalin (EEG, TG) content and soil organic matter carbon content was observed. A periodic application of sewage sludge increased the content of glomalin. However, the highest quality of SOM was found in the control treatment (nonfertilized). This treatment had the highest values for the humic/fulvic acid ratio and the highest contents of humic acids and potentially mineralizable carbon. Furthermore, the Con treatment showed the highest soil aggregate stability and potential wettability index. Mineral N fertilization significantly reduced soil aggregate stability values. Conclusions The unfertilized control showed the highest SOM quality but the lowest yields. The data on glomalin content can be used to study soil organic matter quality. Because the EEG extraction method is easy to apply, uses lower quantities of chemicals and consumes less time, it presents a better option than TG extraction. The sensitivity of the methods for SOM quality determination decreases with increasing SOM content. Graphical Abstract
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Claims 11
Claim · model-written summary
Unfertilized maize yielded significantly less than fertilized treatments.
- Treatment
- fertilization treatmentse0
- Outcome
- average yieldse0
- Direction
- lowere0
- Value
- 9.76 t DM ha −1 year −1e0
- Qualifier
- on average 12.3 DM ha −1 year −1e0
- Comparator
- control treatmente0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The control treatment, which did not include fertilization, showed significantly lower average yields (9.76 t DM ha −1 year −1 ) than the fertilization treatments (on average 12.3 DM ha −1 year −1 ).”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
Yield did not differ significantly among fertilization treatments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant differences in yields were not found between the fertilization treatments.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
Glomalin content correlated positively with soil organic carbon content.
- Compound
- soil organic matter carbone0
- Outcome
- glomalin (EEG, TG) contente0
- Direction
- positive correlatione0
Not reportedTaxon
Verbatim
e0“A positive correlation between glomalin (EEG, TG) content and soil organic matter carbon content was observed.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
Periodic sewage sludge application increased glomalin content.
Not reportedTaxonComparator
Verbatim
e0“A periodic application of sewage sludge increased the content of glomalin.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
The unfertilized control had the highest soil organic matter quality.
Not reportedTaxon
Verbatim
e0“the highest quality of SOM was found in the control treatment (nonfertilized).”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
The control had the highest humic to fulvic acid ratio and humic acid and mineralizable carbon contents.
- Outcome
- humic/fulvic acid ratio and the highest contents of humic acids and potentially mineralizable carbone0
- Direction
- higheste0
Not reportedTaxon
Verbatim
e0“This treatment had the highest values for the humic/fulvic acid ratio and the highest contents of humic acids and potentially mineralizable carbon.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
The control had the highest soil aggregate stability and potential wettability index.
Not reportedTaxon
Verbatim
e0“the Con treatment showed the highest soil aggregate stability and potential wettability index.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
Mineral nitrogen fertilization significantly reduced soil aggregate stability.
Not reportedTaxonComparator
Verbatim
e0“Mineral N fertilization significantly reduced soil aggregate stability values.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
Glomalin content was judged useful for evaluating soil organic matter quality.
Not reportedTaxonComparatorValue
Verbatim
e0“The data on glomalin content can be used to study soil organic matter quality.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
EEG extraction was preferred over TG extraction on ease, chemical use and time.
Not reportedTaxon
Verbatim
e0“Because the EEG extraction method is easy to apply, uses lower quantities of chemicals and consumes less time, it presents a better option than TG extraction.”
e1“maize yield and soil organic matter quality parameters”
Claim · model-written summary
Sensitivity of soil organic matter quality methods declined as SOM content rose.
- Compound
- SOM contente0
- Outcome
- sensitivity of the methods for SOM quality determinatione0
- Direction
- decreasese0
Not reportedTaxon
Verbatim
e0“The sensitivity of the methods for SOM quality determination decreases with increasing SOM content.”
e1“maize yield and soil organic matter quality parameters”
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